48 lines
1.2 KiB
C
48 lines
1.2 KiB
C
#include "tommath_private.h"
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#ifdef BN_MP_SET_DOUBLE_C
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/* LibTomMath, multiple-precision integer library -- Tom St Denis */
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/* SPDX-License-Identifier: Unlicense */
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#if defined(__STDC_IEC_559__) || defined(__GCC_IEC_559)
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mp_err mp_set_double(mp_int *a, double b)
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{
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uint64_t frac;
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int exp;
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mp_err err;
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union {
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double dbl;
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uint64_t bits;
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} cast;
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cast.dbl = b;
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exp = (int)((unsigned)(cast.bits >> 52) & 0x7FFu);
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frac = (cast.bits & ((1uLL << 52) - 1uLL)) | (1uLL << 52);
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if (exp == 0x7FF) { /* +-inf, NaN */
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return MP_VAL;
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}
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exp -= 1023 + 52;
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mp_set_u64(a, frac);
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err = (exp < 0) ? mp_div_2d(a, -exp, a, NULL) : mp_mul_2d(a, exp, a);
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if (err != MP_OKAY) {
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return err;
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}
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if (((cast.bits >> 63) != 0uLL) && !MP_IS_ZERO(a)) {
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a->sign = MP_NEG;
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}
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return MP_OKAY;
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}
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#else
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/* pragma message() not supported by several compilers (in mostly older but still used versions) */
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# ifdef _MSC_VER
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# pragma message("mp_set_double implementation is only available on platforms with IEEE754 floating point format")
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# else
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# warning "mp_set_double implementation is only available on platforms with IEEE754 floating point format"
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# endif
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#endif
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#endif
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